[media] a8293: use i2c_master_send / i2c_master_recv for I2C I/O

As driver is now proper I2C client driver, we could use correct
functions for I2C I/O. Also rename state from priv to dev. Fix
logging too.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>